Phase frequency detecting circuit

Abstract

A phase frequency detecting circuit is designed to produce an output voltage which varies with respect to an input phase difference between a base phase and a reference phase. Herein, a first phase frequency comparator produces a first phase error signal which is proportional to the input phase difference. A first integration circuit performs integration on the first phase error signal to produce a control voltage. Next, a second phase frequency comparator receives a frequency-divided base phase and a frequency-divided reference phase to produce a second phase error signal. A second integration circuit performs integration on the second phase error signal to produce a frequency-divided control voltage. An offset voltage creating circuit creates an offset voltage. Herein, the offset voltage is created based on the frequency-divided control voltage; and a sign thereof is determined responsive to a relationship between the control voltage and frequency-divided control voltage. An offset imparting circuit adds the offset voltage to the frequency-divided control voltage, then, the addition result is amplified to produce the output voltage. Incidentally, an amplifier can be further provided to produce an amplified output voltage based on the frequency-divided control voltage. The amplified output voltage is used instead of the frequency-divided control voltage and is delivered to the offset voltage creating circuit and offset imparting circuit.

What is claimed is: 
     
       1. A phase frequency detecting circuit comprising: a first phase frequency comparator for producing a first phase error signal which is proportional to a difference between a base phase and a reference phase inputted thereto;   a first integration circuit for performing integration on the first phase error signal to produce a control voltage;   an inverter circuit for effecting phase inversion on the base phase to produce an inverted base phase;   a first frequency divider for performing a frequency dividing operation on the inverted base phase to produce a frequency-divided base phase;   a second frequency divider for performing a frequency dividing operation on the reference phase to produce a frequency-divided reference phase;   a second phase frequency comparator for producing a second phase error signal which is proportional to a difference between the frequency-divided base phase and the frequency-divided reference phase;   a second integration circuit for performing integration on the second phase error signal to produce a frequency-divided control voltage;   an offset voltage creating circuit for producing an offset voltage based on the control voltage and the frequency-divided control voltage; and   an offset imparting circuit, receiving said offset voltage and said frequency-divided control voltage, for imparting the offset voltage to the frequency-divided control voltage to produce an output voltage.   
     
     
       2. A phase frequency detecting circuit as defined in claim 1 further comprising an amplifier which amplifies the frequency-divided control voltage, outputted from the second integration circuit, to produce an amplified output voltage, wherein the amplified output voltage is used instead of the frequency-divided control voltage and is delivered to the offset voltage creating circuit and the offset imparting circuit. 
     
     
       3. A phase synchronization circuit comprising: a first phase frequency comparator for producing a first phase error signal which is proportional to a difference between a base phase and a reference phase inputted thereto;   a first integration circuit for performing integration on the first phase error signal to produce a control voltage;   an inverter circuit for effecting phase inversion on the base phase to produce an inverted base phase;   a first frequency divider for performing a frequency dividing operation on the inverted base phase to produce a frequency-divided base phase;   a second frequency divider for performing a frequency dividing operation on the reference phase to produce a frequency-divided reference phase;   a second phase frequency comparator for producing a second phase error signal which is proportional to a difference between the frequency-divided base phase and the frequency-divided reference phase;   a second integration circuit for performing integration on the second phase error signal to produce a frequency-divided control voltage;   an offset voltage creating circuit for producing an offset voltage based on the control voltage and the frequency-divided control voltage;   an offset imparting circuit, receiving said offset voltage and said frequency-divided control voltage, for imparting the offset voltage to the frequency-divided control voltage to produce an output voltage; and   a dependent oscillator whose oscillation frequency is controlled by the output voltage of the offset imparting circuit to produce the reference phase.   
     
     
       4. An angle-modulation phase synchronization circuit comprising: a first phase frequency comparator for producing a first phase error signal which is proportional to a difference between a base phase and a reference phase inputted thereto;   a first integration circuit for performing integration on the first phase error signal to produce a control voltage;   an inverter circuit for effecting phase inversion on the base phase to produce an inverted base phase;   a first frequency divider for performing a frequency dividing operation on the inverted base phase to produce a frequency-divided base phase;   a second frequency divider for performing a frequency dividing operation on the reference phase to produce a frequency-divided reference phase;   a second phase frequency comparator for producing a second phase error signal which is proportional to a difference between the frequency-divided base phase and the frequency-divided reference phase;   a second integration circuit for performing integration on the second phase error signal to produce a frequency-divided control voltage;   an offset voltage creating circuit for producing an offset voltage based on the control voltage and the frequency-divided control voltage;   an offset imparting circuit, receiving said offset voltage and said frequency-divided control voltage, for imparting the offset voltage to the frequency-divided control voltage to produce an output voltage;   an angle-modulation oscillator for producing a modulation signal;   an addition circuit for adding the modulation signal to the output voltage of the offset imparting circuit to produce an addition voltage; and   a dependent oscillator whose oscillation frequency is controlled by the addition voltage of the addition circuit to produce the reference phase which is subjected to angle modulation by the modulation signal.   
     
     
       5. An angle-modulation phase synchronization circuit as defined in claim 4 wherein the angle modulation is either frequency modulation or phase modulation. 
     
     
       6. A phase frequency detecting circuit comprising: a first phase frequency comparator for producing a first phase error signal which is proportional to an input phase difference between a base phase and a reference phase;   a first integration circuit for performing integration on the first phase error signal to produce a first control voltage;   first phase creating means for creating a first phase which is inverse to the base phase and whose frequency is an integral submultiple of a frequency of the base phase;   second phase creating means for creating a second phase whose frequency is an integral submultiple of a frequency of the reference phase;   a second phase frequency comparator for producing a second phase error signal which is proportional to a phase difference between the first phase and the second phase;   a second integration circuit for performing integration on the second phase error signal to produce a second control voltage;   an offset voltage creating circuit for creating an offset voltage whose value is determined in response to the second control voltage, wherein the offset voltage is created together with a sign which is determined responsive to a relationship between the first control voltage and the second control voltage; and   offset imparting circuit for adding the offset voltage to the second control voltage, so that output voltage of the offset imparting circuit is produced by amplifying result of addition by a factor arbitrarily selected.   
     
     
       7. A phase frequency detecting circuit as defined in claim 6 further comprising an amplifier for amplifying the second control voltage by a factor arbitrarily selected to produce a third control voltage, so that the third control voltage is used instead of the second control voltage and is delivered to the offset voltage creating circuit and the offset imparting circuit.   
     
     
       8. A phase frequency detecting circuit as defined in claim 6 wherein the first phase creating means and the second phase creating means are designed to perform frequency dividing operations respectively such that a frequency of the first control voltage becomes substantially double of a frequency of the second control voltage.